This invention relates to flexible couplings for joining two rotatable shafts or other rotating parts which may have their rotation axes endwise or axially misaligned, and deals more particularly with such a coupling which can accommodate a substantial amount of angular and endwise misalignment while transmitting relatively high amounts of torque at relatively high speeds within a relatively small space envelope.
This invention further relates to improvements in the type of coupling shown generally by U.S. Pat. No. 3,481,158; No. 3,521,465; and No. 3,592,021.
In a coupling as shown by these prior patents a number of square, rectangular or other quadrilateral flex members, hereinafter referred to as flex frames, are positioned face-to-face along the central axis of the coupling and are joined to one another at opposite corner portions, and the end frames of the series are similarly connected to driving and driven members, to provide a torque transmitting connection between the driving and driven members wherein angular and endwise misalignment is accommodated by bending of the leg portions of the frames. In these couplings, at a joint between two adjacent frame corner portions, the connected corner portions have parallel bearing surfaces which flatly engage one another and which are held tightly to one another by a threaded fastener passing through aligned corner portion apertures.
The improvement of the invention involves placing a thin flat spacer between the two corner portion bearing surfaces of each joint so as to slightly axially separate the bearing surfaces from one another. Tests show that this inclusion of a thin spacer in each frame-to-frame joint of a coupling surprisingly increases the coupling's performance. In prior design practice, this spacer insertion would have been considered detrimental to the geometry of forces within the joint, generating unwanted bending moments and stresses within the joints. It has been discovered, however, than when thin spacers are used, an unexpected and substantial increase in coupling performance capacity is gained. This gain is felt to be due to an improvement in the flexibility of the flex frame in the area of the interconnecting joint which results from changing the large rectangular clamped area to a smaller circular area. In effect, a greater length of each flexing element is free to bend and twist, resulting in a more even distribution of stresses in the vicinity of the transition between each end of a leg portion and its associated corner portion.
The general object of this invention is therefore to provide, in a flexible coupling of the type having a plurality of flex frames, an improved frame-to-frame connection whereby the performance of the coupling with regard to the range of angular and endwise misalignments it can handle under conditions of high power transmission is substantially increased.
Other objects and advantages of the invention will be apparent from the accompanying drawing and the following description describing a preferred embodiment of the invention.